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    <p>Gevent gives you the ability to deal with blocking requests. It does not give you the ability to run on multi-core.</p> <p>There's only one greenlet (gevent's coroutine) running in a python process at any time. The real benefit of gevent is that it is very powerful when it deals with I/O bottlenecks (which is usually the case for general web apps, web apps serving API endpoints, web-based chat apps or backend and, in general, networked apps). When we do some CPU-heavy computations, there will be <em>no</em> performance-gain from using gevent. When an app is I/O bound, gevent is pure magic.</p> <p>There is one simple rule: Greenlets get switched away whenever an I/O-operation would block or when you do the switch explicitly (e.g. with gevent.sleep() )</p> <p>The built-in python threads actually behave in the same (pseudo) "concurrent" way as gevent's greenlets. </p> <p>The key difference is this - greenlets use cooperative multitasking, where threads use preemptive multitasking. What this means is that a greenlet will never stop executing and "yield" to another greenlet unless it uses certain "yielding" functions (like gevent.socket.socket.recv or gevent.sleep). </p> <p>Threads, on the other hand, will yield to other threads (sometimes unpredictably) based on when the operating system decides to swap them out.</p> <p>And finally, <em>to utilize multi-core in Python</em> - if that's what you want - we have to depend on the multiprocessing module (which is a built-in module in Python). This "gets around GIL". Other alternatives include using Jython or executing tasks in parallel (on different CPUs) using a task queue, e.g. Zeromq.</p> <p>I wrote a very long explanation here - <a href="http://learn-gevent-socketio.readthedocs.org/en/latest/">http://learn-gevent-socketio.readthedocs.org/en/latest/</a>. If you care to dive into the details. :-D</p>
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    1. COI might add that depending on the case, running several Python processes with gevent could be a good solution. Of course this is not an option in case the processes need to communicate with each other in a significant amount.
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    2. COThanks for the answer. What I want is to do as many I/O operations as possible on the machine. The question is: am I capable of doing more requests using n processes (not threads) where n=cpu_cores or is gevent with one process as fast as it can get?
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    3. COHere's how trunk.ly (in the words of Alex Dong) dealt with an I/O-bound AND CPU-bound problem (they crawl sites and then place the crawled content in a search index) - https://groups.google.com/d/msg/gevent/4hR1P6Vd-uk/4A4bw5ynuucJ
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